string str="aaaaaa,bbbbbb,ccccc,ddddd,eeeee";

string[] vtResult=str.Split(',');


string[] _vtResult=Regex.Split(str,",");

------解决方案--------------------
1.字符串直接处理
string input = "aaaaaa,bbbbbb,ccccc,ddddd,eeeee";
string[] s = input.Split(new char[]{','});
for (int n = 0; n < s.Length; n++)
{
	Console.WriteLine(s[n]);
}
2.使用正则表达式
string input = "aaaaaa,bbbbbb,ccccc,ddddd,eeeee";
string pattern = ",";
string[] s = Regex.Split(input, pattern, RegexOptions.IgnoreCase);
for (int n = 0; n < s.Length; n++)
{
	Console.WriteLine(s[n]);
}